For many years people who handle and use flammable fluids such as fuels, large volume chemicals or intermediates have been faced with the serious potential hazards of fire and explosion due to static buildup during filling or unloading of containers such as tanks, due to triboelectric generated discharge, or due to sloshing of the liquids to and fro in tanks during the tank's transportation. Transporting tanks which partially contain flammable fluids, or which contain a small amount of fluid to the extent that the tank is essentially empty, poses the additional hazard of detonation of the fluid due to sparking or static electric discharge caused by the sloshing of the fluids inside the tank. Methods used to prevent sparking and/or static discharge in the tanks include padding the tanks with an inert gas or adding a flame arresting system to the tanks. In addition, physical grounding has been the customary technique for reducing this hazard, however, this technique has not eliminated the problem completely. In addition, human error and poor connections have led to explosions resulting in loss of human life and equipment.
Recently, some containers have been filled with a reticulated open cell polymeric foam in an effort to eliminate the above problems and hazards. One class of foam used heretofore is a polyether urethane which has good chemical resistance, but which has poor static dissipating properties and is flammable in the presence of air. A flame would be present if a container with the polyether urethane foam was to rupture. The other class of foam used heretofore is a polyester urethane which has fairly good static dissipating properties, but has poor hydrolytic properties, poor solvent stability and is also fairly flammable in air. Both of the above classes of foams lose structural properties when exposed to hydrocarbon fuels over a period of time and thus must be replaced regularly.
However, mere sloshing is not the only source of static buildup, and therefore the control of sloshing and, in turn, the control of the static buildup created by the sloshing, alone, does not solve the other problems encountered in tank usage. For example, since such foam materials are not good conductors, they do not discharge a static buildup such as that generated during filling and emptying the container. In addition, such foams are weak structurally and exhibit slow degradation in the presence of most flammable fluids, especially hydrocarbon liquids. This instability problem is increased when small amounts of moisture are present in the container and contact the foam. Another problem frequently encountered in the use of containers with flammable fluids, is cracking or rupturing of the containers due to impact or material fatigue. A crack or rupture in a container will allow flammable fluids to freely escape and pose a dangerous and hazardous condition.
While some success has been obtained by the use of the above-mentioned foams, it would be advantageous for the industry to have a material which, in addition to preventing sloshing, is stable in the presence of flammable fluids, exhibits high electrical conductivity sufficient to dissipate static buildup, and acts as a flame arrester in instances where a spark occurs. Further, it is desirable to have a novel material which is substantially flame resistant and has the capability, when used as a container liner, of greatly retarding the escape of a flammable liquid from the container should the container leak or rupture. Such a novel material is described hereinafter in the accompanying specification and examples.